This application relates to correcting the appearance of vertical tilt caused by rotation of a mechanical galvanometer in relation to the rotation of a photoconductive drum. In particular, this application relates to a beam detection sensor used to correct for the appearance of vertical tilt caused by the rotation of a mechanical galvanometer and the rotation of a photoconductive drum.
Galvanometer use in laser printers has recently increased. A laser printer using a single galvanometer will often have a light reflecting mirror mounted to the galvanometer. In other laser printers, a galvanometer is made from a single silicon wafer and polished to get a mirror finish on an intended reflective surface. The laser printer uses a light source that generates a light beam, which is reflected by the mirror or the polished galvanometer onto a photo-sensitive image forming surface, such as the surface of a photoconductive drum. As the light beam is reflected onto the surface of the photoconductive drum, the galvanometer horizontally rotates the mirror across the photo-sensitive image forming surface. The rotation of the mirror, and the resulting movement of the light beam across the photo-sensitive image forming surface, produces forward-going and reverse-going scanlines.
However, while the galvanometer is horizontally rotating the mirror, the photoconductive drum is rotating vertically. Due to the movements of both the galvanometer and the photoconductive drum, the resulting forward-going and reverse-going scanlines are often vertically tilted with respect to each other. Laser printers that use a galvanometer to produce forward-going and reverse-going scanlines often do not account for the vertical tilt caused by the rotation of the galvanometer and the photoconductive drum, and are unable to determine this vertical tilt.